Modern ink makes the Apple Watch think you're dead.
CNN reports the new Apple Watch needs your pulse to work. Unfortunately tattoo ink gets in the way:
According to Apple, the back of the Watch rapidly flashes green and infrared light at your skin, which gets absorbed or reflected by your red blood. When your heart beats, there is more blood in your wrist, and there is less blood between beats. By sensing the timing between your heartbeats, the Apple Watch can calculate your heart rate.
As it turns out, solid-colored tattoos -- particularly red ones -- also absorb the green light and reflect red light. Black tattoos, which absorb both green and red light, can also screw up the Apple Watch's heart rate sensor.
The impact for an apparently-not-so-alive user: no phone calls, no notifications, no Apple Pay.